Actually, Raw Chicken Likely Can Lead to Paralysis in Dogs.

I recently reported on a study out of Australia that found an association between feeding raw chicken, infection with the bacterium Campylobacter, and a serious neurologic disease call Acute Polyradiculoneuritis (APN). Not surprisingly, advocates of raw diets are desperate to find ways to dismiss this study so they can continue to claim raw diets are as safe, or safer than commercial cooked pet foods. Cognitive dissonance, the discomfort that one feels when confronted with evidence that one’s beliefs about something may be wrong, is a powerful force, and it can lead even smart, educated people to engage in extreme mental gymnastics to dismiss such evidence and preserve cherished beliefs.

Many of the criticisms of the Australian study are simplistic and obviously wrong or irrelevant. It is sometimes dismissed as ”just one study.” This would be a fair criticism if it were true and if there were substantial evidence of benefits to feeding raw that balanced the potential risks, but unfortunately neither of these is the case. There is abundant and robust evidence that raw meat poses a greater risk for infectious disease and parasites than cooked meat, both in terms of studies of contamination of raw pet foods (1,2,3,4,5,6) and the overwhelming evidence in humans that handling and eating raw meat increases these risks and cooking reduces them. It is simply a fact that raw meat is more dangerous than cooked meat, and there is no good argument or evidence that this is not true for pets as it is for people.

A more complex attempt to dismiss the APN findings, and one which is getting some attention online, comes from a raw feeding advocate (and perhaps not surprisingly a marketer of raw foods and other alternative health products), Dr. Conor Brady.

Dr. Brady has a PhD in animal behavior and states that is research focus involved nutrition, so one would expect him to at least present a scientifically reasonable argument. Any study has limitations, and the Australian APN study is no exception, so a science-based critique would be a normal and welcome part of the scientific process.

Sadly, this is not what Dr. Brady offers. Instead, he lurches from scientifically sloppy arguments to cherry-picking of evidence to empty ad hominem attacks on the pet food industry. What he fails to do is provide any real reason to doubt the findings of the APN study.

What Does the Australian Study Actually Say?

Let’s start by looking at what the APN study actually says. The core of the argument made in the study is this:

Up to 40% of Guillain-Barre Syndrome (GBS) cases in humans may be triggered by the bacterium Campylobacter.

Most Campylobacter infections in humans come from eating or handling raw poultry.

APN is believed to be a canine version of GBS, so the study sought to see whether there was an association between APN, Campylobacter, and eating raw chicken.

APN did turn out to be associated with Campylobacter. 48% of dogs with APN had this bacterium while only 23% of healthy digs did. When looking at recent Campylobacter infections, which would be the most likely to serve as a trigger for autoimmune diseases like APN, three times as many APN dogs had it compared with control dogs.

APN was also associated with feeding raw chicken. 96% of APN dogs were fed raw chicken while only 26% of control dogs were. Only 1 APN case was not fed raw chicken, and this dog had daily contact with live poultry.

Give these clear associations, it is likely that Campylobacter acquired from raw chicken is a trigger for some APN cases, as it is a trigger for GBS in humans. There are likely other triggers as well, but in this population of dogs feeding raw chicken seems a clear risk factor which would be easily eliminated. If there were clear and proven benefits to feeding raw chicken that outweighed this risk, it might still make sense to do so, but no such benefits have ever been demonstrated.

Dr. Brady’s Attempted Rebuttal

So now let’s turn to Dr. Brady’s comments on this study. He begins reasonably enough by acknowledging that Campylobacter is a serious infectious organism and that raw chicken is a common source for it:

Raw chicken is certainly a source of Campylobacter and a lot of raw dog foods are based on raw chicken. What’s more, Campylobacter is well known to put you on your ass, or at least pooing a lot out of it. It is the most common bacterial cause of enteric disease worldwide, with two million American cases reported annually.

From there, though, he goes through a series of objections which range from reasonable but misleading to completely ridiculous. Let’s take each in turn.

Do most dogs have Campylobacter in their intestines regardless of what they are fed?

The prevalence of Campylobcater in healthy dogs varies. Some studies show rates from 25-58%, as Dr. Brady claims, but others show much lower rates (such as this study in Poland with infection rates < 5%). Dr. Brady is being misleading, however, in suggesting that the rate in the Australian APN study was irrelevant because it was “normal” or the same as in normal dogs in Australia. The only other study looking and Campy in Australian used mostly stray dogs, which obviously have different diets and health status from owned pet dogs.

Certainly, not all dogs with Campylobacter will get sick, and not all varieties of Campylobacter are pathogenic. However, that has little to do with the results of the APN study. The dogs with APN still had Campy at a much higher rate than the dogs without APN, and this difference doesn’t magically go away just because other dogs in other places have had Campylobaxcter without having APN. As Dr. Brady acknowledges, Campylobacter is a potentially serious infection often acquired by exposure to raw chicken, and this remains true even if some strains are worse than others and not all dogs exposed to it get sick.

There are many potential triggers for GBS and APN.

So what? If Campy from eating raw chicken is a risk factor (potentially causing 40% of human GBS cases), shouldn’t we do what we can to eliminate this and reduce the risk? Dr. Brady’s argument is like saying that because some people die in car crashes from reasons other than not wearing a seatbelt, we can ignore the fact that not wearing a seat belt is a major reason people do die in car wrecks. Medicine and public health are about reducing risk where we can, not creating a risk-free world. Until there is evidence of benefit from feeding raw meat (and right now there isn’t!), doing so despite the risk of diseases like Campy and APN makes no sense.

Dr. Brady makes a number of misleading or false statements in this section of his post. For one, he cites a paper that found no association between APN and Campylobacter to suggest this contradicts the Australian study. What he ignores is the fact that the paper he cites studied an entirely different population of dogs in another part of the world, it used less reliable measures of Campylobacter infection (serology rather than culture and PCR), and none of the dogs in that study were fed raw meat. In implying that this paper undermines the conclusion of the Australian study, Dr. Brady is either being disingenuous or showing a lack of understanding of basic principles in science and epidemiology.

Interestingly, the study he cites here implicated a different pathogen, Toxoplasma, as a potential trigger for APN. Since this parasite is also mostly acquired in humans from eating undercooked meat, this would actually provide another reason to avoid feeding raw meat to dogs. Dr. Brady cherry picks not only the studies he cites but the parts of them he refers to.

Brady also mentions vaccinations as a potential trigger for APN. In doing so, he cites a case report, which is a much lower level of evidence than the Australian case-control study he is dismissing here. He chooses which evidence to accept and which to reject based primarily on what agrees with his beliefs, not objective scientific criteria for the strength of the evidence.

Even more ridiculous is Dr. Brady’s reference to a study he suggest shows that APN can occur in dogs not even being fed “real food” but still nursing (how mother’s milk is not “real food” isn’t made clear). The study he cites, however, is actually a case report of dogs with a protozoal parasite invading their brains and causing neurologic symptoms, which is not even the same disease as the immune-mediated APN in the Australian study. This fast-and-loose approach to scientific evidence is another example of how Brady seeks only to legitimize his existing beliefs with reference to cherry-picked or misconstrued research, not to really listen to the evidence.

Was the study too small or poorly done?

The short answer is, “No.” Sample size is always an issue in veterinary research, especially when studying uncommon diseases like APN. Most of the time, too small a sample either leads to false negative results due to low statistical power (that is, not finding something that is actually true because you didn’t have enough examples to get a statistically significant result). The other problem with small samples is that random variation between individuals can more easily lead to the appearance of differences between groups that don’t really exist. If you measure the height of five people to determine the average height in the entire country, a sample that includes only men or only NBA basketball players is likely to give you a result that doesn’t accurately reflect the whole population.

A larger sample would certainly strengthen the results of the APN study, but the results were quite consistent and distinctive even with the numbers used. The results were also consistent with the existing evidence regarding the link between Campy and eating raw chicken as well as the link between Campy and GBS in humans. To borrow a phrase from Dr. Brady, it is “extremely unlikely” that the results of this study are due to chance effects from a small sample population.

His second criticism is less reasonable and betrays a surprising lack of understanding of research methods for someone with a PhD. He complains that the control group was not selected “randomly.” He is correct that it was not, but he is confusing this study, which was a case-control study, with a randomized clinical trial, which is a very different design with different methods.

In a case control study, you start by collecting patients with the disease you are interested in. This is commonly done for rare diseases because simply studying a bunch of patients at random would likely never give you enough cases to learn anything from. Once you have your cases, you select controls that are matched to your cases so that they are likely to be representative of the same group that the cases came from. That means deliberately looking for patients with similarities to the patients with the disease such as age, sex, race, etc. This is not a mistake, it is a core feature of the type of study being done.

Dr. Brady then makes a bunch of comments about how the case selection method invalidates the results which illustrate that he doesn’t understand very well the research methods he is critiquing. He complains that selecting staff pets means they aren’t comparable to the APN dogs because they were less likely to be fed raw chicken. However, the fact that dogs without APN are less likely to be fed raw than dogs who are eating raw meat is exactly the thing being studied. If the control dogs and the APN dogs were all eating raw, there would be no way to tell if this was a risk factor or not!

Similarly, Brady complains that the dogs were not matched on weight, implying again this invalidates the results. But once again, this was a deliberate part of the design to allow the investigation of weight as a potential risk factor, as is actually explained in the published study report: “Very coarse frequency matching by dog size (so that this variable could still later be analyzed for associations with case-control status).” It turned out that weight wasn’t a risk factor associated with APN anyway, but breed size category was. Small breeds were more likely to be APN cases that larger breeds.

Now, the authors hypothesized this might be because small breeds were more likely to be fed raw chicken and get Campylobacter, which are the main risk factors associated with APN in this study. Dr. Brady seems to agree that small breeds are more likely to be fed raw chicken, but he makes the odd conclusion that instead of this leading to Campy infection which triggers APN, small dogs are more likely to get APN for some other reason and the fact they eat raw chicken more often is unrelated.

If this is true, then of course we have to ignore all the evidence of association between Campy and GBS and between raw chicken and Campy and just assume there is some other reason small breed dogs get more APN. This is not supported by any reasoning or evidence. It is ultimately just a guess intended to deflect any potential acknowledgement of the risks of raw feeding.

4. Couldn’t Campy in APN dogs be due to something else? Anything else?! ANYTHING BUT RAW!!

At this point, Dr. Brady loses even basic coherence in his argument. He asks the rhetorical question “Might there be another reason dogs with APN shed Campylobacter” and proceeds to admit he doesn’t know, but he is willing to speculate wildly so long as the reason is anything but feeding raw meat. All the evidence that eating raw meat is associated with Campy in humans and other animals is ignored as he grasps at straws to find another answer more compatible with his faith in raw feeding.

He meanders into unsubstantiated musings about reverse causality, suggesting APN weakens the immune system which leads to Campy infection. This is clearly nonsense since APN is an inappropriate immune system reaction, not a weakened immune system, and the overwhelming majority of Campy is associated with eating raw meat in people and dogs without APN.

Brady then launches into a tirade about the evil of feeding dogs carbohydrates that has absolutely nothing to due with Campy, APN, and the Australian study. This is simply hand-waving to distract from the lack of a coherent explanation for the study findings. He also turns the lack of evidence for raw feeding on its head, suggesting that the lack of any research evidence showing health benefits to feeding raw rather than conventional diets is actually a reason to choose raw diets. Talk about smoke and mirrors! The decades of research on conventional diets is casually dismissed by reference to “industry,” which is not only silly but hypocritical for someone who makes his living selling unproven supplements, diets, and dietary advice.

Finally, he launches into a lofty rhetorical assault on the pet food industry, full of sound and fury but also full of bullshit and woefully lacking in facts. Here is a brief sample:

Lacking any evidence to support the use of their junk food products over fresh ingredients, all they have left to convince you to hand over €5 per kilo for what is Weetabix with cows toenail and crushed centrum tablet in it, is smoke and mirrors. And the best smoke is fear. Fear you will do it wrong. Fear they will get sick. Fear you will get sick. Fear your kids will get sick.

…as cereal-based dry food sales stutter and fall worldwide, to be replaced by more natural, raw dog food products not yet owned by them, the multi-billion industry is not going to go down without a fight. The notion of fear and danger will keep coming up, more and more in the future. ..while raw dog food is yet to kill a dog or harm a single human, dry food cannot say the same in either instance. Injury aside, dry foods’ body count from chemical and microbiological contamination is absolutely shocking.

There isn’t a dry-versus-raw debate guys, any more than there is a global warming debate. There is only skewed, industry nonsense and everyone else. Fear is their weapon. Truth is their enemy. The really scary bit is that what is true and what is industry-nonsense will become harder and harder to detect.

Actually, I find the really scary bit to be the ability of a smart, scientifically educated person like Dr. Brady to ignore and distort evidence to preserve his beliefs at any cost. One can speculate on the financial motives that might influence his thinking, as he clearly believes it influences the thinking of anyone who dares to disagree with him, but I actually doubt that’s a major factor. I think he is simply a true believer who fancies himself a brave warrior against the Evil Empire and is unable to accept any facts that might undermine that belief. The real scary bit is that people might belief the rhetoric and the distortions and suffer for it. Despite his bold claim to the contrary, raw food can harm your pets and you and, yes, your children. Here is just one recent example:

The Minnesota Department of Health reports that two children in a single household were exposed to contaminated Raws for Paws product, which was used to feed the family dog. One child’s illness resulted in septicemia (blood infection) and osteomyelitis, a painful and serious bone infection.

Testing performed by the Minnesota Department of Health and the Minnesota Department of Agriculture demonstrated that the same strain of S. Reading found in the ill children was also found in four samples of Raws for Paws Ground Turkey Food for Pets that was used to feed the family pet.

Dr. Brady can call me a dupe or lackey of Big Pet Food if he wants (and I suspect he will). The truth is, I am open to the idea that fresh food, even raw food, might have health benefits. However, the evidence is clear that raw has risks, and it is up to the proponents of raw diets to prove there are benefits that make these risks worth taking. Not with anecdotes, faulty logic about what is “natural,” rhetorical assaults on the pet food industry, or mere passion. They should prove it with data, with reliable evidence derived from appropriate scientific research. Until they do so, there is no reason for pet owners to take the risks they deny exist for ourselves, our pets, or our families.

22 Responses to Actually, Raw Chicken Likely Can Lead to Paralysis in Dogs.

I actually read about another example. A foster mom was feeding her dog a frozen raw diet. The boy got salmonella playing with the dog, and the child welfare agency was able to link the salmonella to the frozen raw food diet and in order to keep fostering the boy, she had to feed the dog something different.

“Basically what they eat I eat.”
And you eat your meat raw? Certainly early humans did, so it’s as much a part of out evolutionary history as it is of that of our pets. Cooking is arguably as unnatural for us as them.

As for the idea that you can just ignore all evidence because you think it is funded by some commercial conspiracy, that’s just a rationalization for ignoring evidence that conflicts with your beliefs. Everyone has bias, whether financial or ideological, and that applies to raw advocates and folks selling raw foods as much as to companies selling cooked foods. You pick and choose what kinds of bias to care about so that you don’t have to consider changing your mind. You ignore all the biases that make personal experience and anecdote unreliable, but you care about funding bias in research because that leaves your beliefs unchallenged. It’s a pretty clear example of confirmation bias.

“Wouldn’t it be more helpful to ascertain and advise them appropriately Instead of their blanket raw is bad.”
Not if the truth is that raw has no benefits and only risks. As I’ve said, I’m open to any scientific evidence that there are benefits worth the risks, but unless this is produced, the most reasonable approach is to avoid the risk altogether.

Your analysis of the data out there and the comments that follow have convinced me. When you’re right, you’re right. I feed raw meat to my cats, but I think your arguments apply to them as well, and I want to stop their raw diet. However, there is so much conflicting information on the web, it’s hard to figure out what is a good replacement. Do you have any information on what to look for when it comes to finding the right diet for my cats?

Unfortunately, there is no simple way to choose the optimal diet for any individual. Assuming healthy adult cats, a balanced reputable commercial diet is a good starting place, though it is important to monitor weight, coat quality, stool quality, and other general indicators of condition since some individuals may do better on one food than another even if both are equally good foods in general. There is at least a plausible argument that canned is better than dry in terms of moisture and carbohydrate content, and it is certainly lower in calories, which can reduce obesity. Beyond that, there is no compelling evidence to support the claim of every brand that they are superior to every other brand, just marketing hype.

Excellent commentary, as usual.
At the moment we have three dogs who are raw fed for various reasons. The other six aren’t (they are fed a high quality, high protein commercial diet with added cooked bits for interest).
However, having looked at your blog and the science behind it, rather than the original research, I’m looking at alternatives. Freeze dried maybe? Cooked/tinned perhaps? At least when the elderly greyhound who won’t eat anything other than raw finally pops off the planet!

Hello there. I *really* admire and enjoy your blog posts. I have forwarded a link to this latest one to several more junior colleagues who are very interested in this topic.

We discussed the Melbourne / APN / Campy / raw chicken study at Journal Club this week. I concur with 98% of what you have written above, and I think the fundamental findings of the study are sound, but I would appreciate your comments on this one point:

I think the study would have been stronger if each control dog was chosen from the same neighbourhood as its matching case. I base this on a view about case-control studies: “Controls should come from the same population as the cases, and their selection should be independent of the exposures of interest.” Schulz KF, Grimes DA (2002). “Case-control studies: research in reverse”. Lancet. 359 (9304): 431–4.

I am not convinced that using veterinary staff-owned animals as controls complied sufficiently with the requirement for independence from the exposure of interest (in this case, the feeding of raw chicken). I do not agree completely with the way you wrote about the nature and design of case-control studies in this excellent rebuttal.

Once again, I find your work on this blog outstandingly good and very enjoyable.

Thanks for the comment and question! I think the limitation you refer to is a real one, and it has to be factored into the process of setting our level of confidence in the findings, as is always part of the critical appraisal process. This, then, gets factored into the larger context to help make real-world decisions.

The trick with a case-control study is to pick a control population that is representative of the population that produced the cases except for the exposure of interest. The authors of this study stated their variables of interest to be “the association between Campylobacter infection in dogs and APN [and] to identify potential risk factors associated with APN, including consumption of raw chicken meat and recent Campylobacter infection.” For this purpose, selection of the control group should be independent of exposure to raw chicken.

The control groups was described as being “either client-owned or staff-owned.” It doesn’t appear they specifically excluded staff-owned dogs from the case group, but since APN is rare it is unlikely any of the cases were staff owned. So the question, then, how many control dogs were staff-owned, and does having staff-owned animals included in the control group make these dogs unrepresentative of the population that produced the cases? Would this potentially change the associations seen in the study?

I don’t think there is a simple way to definitively answer these questions. I can see that being a staff-owned pet would potentially be associated with a reduced likelihood of eating raw chicken since feeding raw is less popular among veterinary professionals than the general public. If this is true, then fewer dogs in the control group would be eating raw chicken than in the case group, and the association might appear stronger that it really is. However, this requires a our assumptions to be true: 1. a significant proportion of the control group were staff-owned, 2. staff pets are less likely to eat raw chicken than pets owner by the general public. These are just suppositions, not known facts.

This particular concern could, you are right, be eliminated by ensuring no staff-owned pets in the control group. However, there are inevitably potential differences between control and case groups in any case-control study, and I suspect the proponents of raw diets would seize on others to make the same argument. We cannot eliminate weaknesses entirely from research studies, which is why biologic plausibility and consistency across different kinds of evidence are critical for establishing causal relationships. The association between Campy and GBS in humans adds to the strength of the hypothesis advanced in this study. Of course, no single study is ever definitive, and there is room for some uncertainty in the hypothesis that raw chicken leads to Campy which leads to APN. More studies, ideally with different design features and limitations, would certainly strengthen the hypothesis (or potentially weaken it). All-in-all, I think it is a pretty good piece of evidence suggesting one more potential risk to feeding raw chicken, but the overall case against feeding raw certainly doesn’t hinge on this one study.

For me, the larger issue is are there potential risks to raw diets, and how do these compare to the potential benefits. This study is just one piece of a larger picture of evidence supporting the rather obvious view that eating raw meat poses health risks. Against this I have yet to see objective evidence of benefits, so I remain unconvinced that the risks are worth taking.

I’ll make this brief. Your entire theory is flawed from the start because you cannot compare the human digestive system to that of a dog. They are completely different. Dogs intestinal tracts are much shorter and designed to process meat rapidly. Dogs carry the salmonella bacteria too, which would harm humans but doesn’t bother dogs. I have been feeding raw for almost twenty years and yes, there IS a standard. Your dog’s diet should mirror that of a prey animal…generally considered to be 70% bones, 20% muscle meat and 10% organs. That, as I said, is a very brief explanation, although I could go on for pages. Commercial dog foods get recalled regularly. My dogs’ food is bought at the supermarket, the same meats that humans eat. It’s just not cooked. And the reason you don’t see a lot of studies? That’s easy. No money in it, not for the dog food manufacturers or the veterinary establishment.

I understand you believe that dogs are immune to Salmonella due to their natural history and anatomy, but this isn’t actually true. Some types of Salmonella can be harbored without symptoms, others are more likely to be pathogenic, and individuals with other illnesses, parasites, or who are very young or old, may be more susceptible. In addition, dogs can shed salmonella which can harm humans even if it doesn’t harm the dogs, and raw feeding increases this risk. Your anecdotal experience is not, as you seem to believe, convincing evidence for your claims. The risks to pets and humans are real, and there are no proven benefits to justify the risks.

As for the idea that we can do without research because there is no money to be made on raw foods, you are wrong on two counts. There are, of course, plenty of people making money off of commercial raw diets and off books and lecture tours selling raw feeding. They could pay for studies if they really wanted to. And regardless of the reasons for the lack of evidence, without that evidence we still can’t know the truth, so you can’t simply get away with claiming that you are right and you don’t need to bother proving it since it is too expensive to do so.

Carole, go to FDA-CVM and compare the number of raw pet foods recalled to commercial foods (there’s been quite a few this year alone, as compared to commercial).

Raw food can contaminate you, your pets, your kids and anyone who comes into contact with infected pets or surfaces or objects – if your dog is infected, one of your guests gets a kiss from your dog, that guest can become infected and ….

Do you really think that a supermarket is immune to contaminated products?

When I switched my dogs to raw food, I was able to do it overnight. No very changeover which I have found to be necessary when switching from one processed food to another – good brands all. Also the dogs’ poops on raw are way better – less soft, less smelly and less of it. Finally with raw I have no problem with the dogs’ weight. They are lean but not skinny. Before I switched to raw one of my dogs often vomited. He still does but occasionally, but very much less. The evidence of my own dogs suggests to me that raw food is best.

Greetings and thank you for your thorough and thought-provoking comments on raw feeding. What do you think about companies using High-Pressure Processing of raw pet foods to make them “safer”? While raw-food purists complain that good bacteria is destroyed along with harmful bacteria (as well as a number of other complaints) is still seems to have some promise in making the practise of raw feeding at least a little safer. I am a pet supply store owner and I carry raw products like this (originally due to two vets asking for these products) as a means of attempting to provide some protection for pets and their owners. While it still makes no claim to the efficacy of a raw diet do you think HPP is at least a step in the right direction?

though there isn’t much data on commercial raw diets specifically, in general it seems like HPP likely does reduce the risk of bacterial contamination significantly. Whether there are any benefits to feeding raw, and whether these are reduced by HPP, is still a matter of opinion for the most part since there is almost no real evidence.

hi, dis you study ever say any other way to get rid of this problem without cooking the meat? because it would be something im willing to do, vut i already know i wont ever have time to properly cook it, unless i had a pressure cooker, which i dont ( due to the fact that cooking bones any other way will make them sharp and splintery, while in a pressure cooker, chicken bones turn to mush ( only had success with chicken bones tho)) while still retaining nutrients. is it possible to sterlize the meat via freezing or anything?

The craze with raw feeding is ridiculous, and from my experience, many of
these same crazed people have gone down the magical pseudoscience path of
paleo, LCHF, keto etc., for themselves thinking their weight loss was
because of *insert eating method* instead of a reduction in calories through
demonizing/removing a particular macronutrient.

One successful raw pet food company (based out of Portland, Maine) claimed,
and I quote, “The Food and Drug Administration recently released an article
informing the public that “salmonella is not harmful to dogs.” The acidity
level in the canine stomach is very high, creating a very inhospitable
environment for bacteria.”

When asked for their source on said claim they skirted around the
topic and instead offered me a discount toward their product, ha. I submitted a Pet Food Safety Report through the FDA and
surprisingly, either through sheer luck or coincidence, that claim has since been revised and no longer includes
mention of the FDA. Thanks for doing what you do, Brennen and please keep
fighting this battle. Those of us who are evidence based appreciate you.